chore: remove std directory (#9361)

This removes the std folder from the tree.

Various parts of the tests are pretty tightly dependent 
on std (47 direct imports and 75 indirect imports, not 
counting the cli tests that use them as fixtures) so I've 
added std as a submodule for now.

1 files changed, 0 insertions, 0 deletions

diff --git a/test_util/std b/test_util/std
new file mode 160000
+Subproject 5ae977b81ff1522f73301bc87f929dbdc0d6954